Metabolic diseases such as diabetes affect the lives of millions of people. Many of these diseases may be controlled by administration of a particular enzyme, hormone, or other agent. Some of these agents can be ingested as pills or syrups. Others, such as insulin, must be injected daily or even more frequently. Diseases such as diabetes also require constant monitoring of the blood levels of certain molecules. For example, diabetes patients must give themselves multiple finger pricks every day to monitor their glucose levels.
Administration of pills or injected insulin may result in uneven blood concentrations of insulin or other agents over the course of a day. For example, most pills result in a spike in blood concentrations of a drug. These concentrations decrease over time to levels that are not therapeutically effective. In addition, it takes time for agents administered as a pill or even an injection to circulate throughout the body. However, the appropriate levels of metabolic agents or hormones changes over time. Thus, while the average serum levels may be appropriate for the patient, the instant serum concentration of the drug is not optimal at any specific time. As a result, it is desirable to have a drug delivery method that provides a therapeutic agent in the quantities and at the times required by a particular patient.